OF NORTH AMERICA. 277 



from the side; retractor muscles of penis two in number, very long 

 and narrow, ribbon-like; one muscle enters the penis-sac and one the 

 head of the penis ; protractor muscles very small, five in number, three 

 on the posterior and two on the anterior face of the penis-sac. 



Female organs: Oviduct not differing from that organ as found 

 in other Lymnreas; receptaculum seminis not remarkably large, ovate 

 or pyriform, with a duct 3.00 mill, long joining the oviduct .25 mill, 

 from the vaginal opening; albuminiparous gland of the usual form; 

 first accessory albuminiparous gland large, pyriform, a little elongated, 

 its proximal end narrowing suddenly toward the vaginal portion of 

 the oviduct. The receptaculum seminis is orange in color and the 

 albuminiparous gland is yellowish. 



The genitalia exhibit some variation. The retractor muscle of the 

 male organ may be separated or the penis retractor may enter the 

 penis-sac retractor about half its length from the columellar muscle. 

 (PI. XIV, fig. G, 1, 2.) The first albuminiparous gland also varied 

 in one specimen, being irregularly quadrate instead of regularly pyri- 

 form. In another specimen the prostate was flattened and broadly 

 pyriform when viewed from above, but elongated when viewed from 

 the side. (PI. XII, fig. C.) The majority of specimens examined, 

 however, were as shown in figure C, plate XI. 



Several measurements of the genitalia gave the following results. 

 (Dissections Nos. 23167, 23168, 23169, 23170, 23177, 23178, 23179.) 

 The uniformity of the majority of the measurements is noteworthy. 



Penis- Rec. Prost. Vas. Ret. mus. Ret. mus. 



. Shell. 



9.50 Cayuga Lake 1 

 11.50 " J 



10.50 Sea Breeze 1 

 11.50 J 



11.50 Des Moines 

 13.00 

 11.50 

 12.00 Narrow form 



9.00 

 10.00 



On May 15, 1907, several egg masses were laid by this species 

 in an aquarium ; the measurements of the masses and the number of 

 eggs in each are given below : 



800x2.00 mill., 30 eggs; 7.50x2.50 mill., 45 eggs. 



RANGE (Figure 28) : From the Atlantic to the Pacific oceans, 



Animals killed in June. 



